Last week's Connecticut shooting has once again focused the national spotlight on assault weapons and their place in America.

Everyone has heard of these guns. They've been available to the U.S. public for generations. Understanding where they came from goes a long way to understanding that they're not going away any time soon.

As soon as gunpowder was poured down a metal tube and lit to fire a bullet, the challenge became speeding the process along.

When colonial settlers in America took up arms against the British, technology was still where it had been when rifles were first introduced. Pour the powder down the barrel, tamp it down with a metal rod, shove in a ball of lead, and wait for the spark from the trigger to reach the powder in the barrel.

With this technology, the best soldiers could get off approximately 3 or 4 rounds a minute, and those rounds — sphere-shaped lead balls — had little accuracy.

The smooth bore of old rifles sent rounds jumping through the air like a baseball pitcher's knuckleball. Hitting a target was hard, and the inaccuracy of these guns was part of the reason British soldiers lined up to fire in unison, like they do in the movies.

The more standardized Minié round also allowed inventors to construct a feeding mechanism that drastically streamlined the loading and firing process.

Inventor Benjamin Tyler Henry, created the Henry Repeating Rifle in 1862, and "semi-automatic weapons" were born.Though the Henry repeater isn't a modern semi-automatic (it still had to be cocked before every shot, versus a true semi-automatic, which cocks itself and fires a round with every trigger pull), it allowed rapid firing of rounds up to about 12 a minute.

The invention was the Atom Bomb of the 1800s military world, and it set the stage for the beginning of American arms making.

"What saved us that day was the fact that we had a number of Henry rifles," Major William Ludlow's wrote in his account of the Battle of Altoona Pass during the Civil War. "This company of 16 shooters sprang to the parapet and poured out such a multiplied, rapid and deadly fire, that no men could stand in front of it and no serious effort was made thereafter to take the fort by assault."

Rifle technology remained, for the most part, unchanged over the next 50 or 60 years (there were slight modifications and enhancements, but the guns still had to be cocked for every shot).

What innovations there were came mostly in the field of automatic weapons, which were clunky and required Wikimedia Commons

at least two men to operate — like the infamous Gatling Gun, which required a cranking system and often fell victim to double feed and jams.

When World War I came around, ground troops were still largely using bolt-action one shot rifles, and shots per minute remained about the same as the days of Henry, about 12 per minute. The world was in desperate need of a rapid-fire rifle for light infantrymen.

There came the Winchester Model 1905, a "self loading" rifle, as they were called back then, that fired a bullet with every pull of the trigger. One key difference though was that these rifles had to be loaded like modern shotguns, with each shell manually fed into the rifle via a port on the side.

The manual loading made it difficult for troops under fire to reload and return fire. What the Army needed was self contained magazine style loading.

The M1 Garand came around the end of the World War I, and for the first time soldiers used small preloaded 'clips' or 'cartridges' that held eight rounds each. This was no assault rifle, and soldiers had to fire all eight rounds in the clip before reloading, which left them in a bind if they took cover with only one round left in the weapon. But it was a huge step up from manual shooting.

The BAR was a light infantry machine gun, which would later serve as inspiration for the light squad automatic weapons still used today.

The M1 Carbine came years later, in the early 1940s, as part of an Army initiative to provide soldiers with a light assault carbine that stored rounds in several interchangeable magazines. The M1 Carbine was the first magazine loaded, light semi-automatic weapon — and all designs since then, M16s and AK-47s, are based on this original rifle style.

In the history of weapons, the M1 Carbine is the father of what all of we now call "assault weapons." It is also something the writers of the U.S. constitution probably never imagined.